There are widely employed, as packaging materials for a variety of articles in the fields of foods, pharmaceuticals, electronic part items and the like, bag bodies each fitted with a plastic zipper. In particular, there are widely employed plastic zippers each equipped with a slider because of easiness in opening and closing and its capability of resealing. Thus, accompanying the diversification of objects to be packaged, it follows that higher hermetical-sealability is required of the plastic zippers. At the same time, it is desired that the zipper be endowed with the function capable of detection of its having been unsealed after sealing packaging, since unsealing thereafter due to an unfair purpose or mistake brings about such disadvantages as foreign matters being mixed in and impaired quality of the content in the bag bodies.
FIG. 9 through FIG. 15 each illustrate an example of a previously known plastic zipper which is equipped with a slider, and is endowed with high hermetical-sealability and/or function capable of detecting unsealing.
The example as illustrated on FIG. 9 (perspective view) and FIG. 10 (cross sectional end view taken along line A–A′ of FIG. 9) point out a system wherein the top portion of a bag body fitted with a zipper in which a bag 9-3 is fitted with a zipper 9-2 and a slider 9-1 is covered with a cover film 9-4 bearing perforated line 9-5 so that the portions of the slider and zipper are overspread therewith, and in the case of unsealing for the first time, the perforated line 9-5 are cut off and thereafter the zipper is opened/closed by means of the slider. The above-mentioned system has simple structure and favorable operability, but suffers from such disadvantages as unfavorable appearance and inferior productivity from the industrial viewpoint.
The example as illustrated on FIG. 11 (perspective view) and FIG. 12 (cross sectional end view taken along line B–B′ of FIG. 11) point out a system wherein a partition film 11-4 bearing perforated line 11-5 is installed inside a bag body fitted with a zipper in which a bag 9-3 is fitted with a zipper 9-2 and a slider 9-1, and in the case of unsealing for the first time, the zipper is opened by means of the slider and thereafter, the perforated line 11-5 are opened. The above-mentioned system has favorable appearance and good productivity, but involves such a problem that in the case of the content being fine particles such as powder, the partition film portion is plugged up with the fine particles, thereby making it impossible to smoothly discharge the same.
The example as illustrated on FIG. 13 (perspective view) indicates a system wherein a bag body fitted with a zipper in which a bag 9-3 is fitted with a zipper 9-2 and a slider 9-1 is subjected to spot welding (13-1) at the top portion of the zipper in a state that the slider is at the closing position, and in the case of unsealing for the first time, the weld portion is cut away with the slider.
The method as illustrated on FIG. 14 (perspective view) indicates a system wherein part of a zipper top portion 14-4 bearing perforated line 14-5, etc. is cut off in a state that the zipper 9-2 is set at the closing position of the bag 9-3, a slider is attached to the cut portion, and in the case of unsealing, the zipper top portion 14-4 is cut away along the perforated line.
The systems as illustrated on FIG. 9 and FIG. 11 is advantageous in that the hermetical sealability of the bag body can be assured by the adoption of the hermetical-sealed perforated line, whereas the systems as illustrated on FIG. 13 and FIG. 14, the hermetical sealability of the bag body depends upon the hermetical sealability of the zipper itself, thus making the above-cited systems unusable in applications based on the precondition of long-term preservation such as retort pouch.